1. Field of the Invention
The present invention generally relates to a wireless communication system, and more particularly to a Low Density Parity Check (LDPC) code-based Hybrid Automatic Repeat Request (HARQ) method.
2. Description of the Related Art
In a wireless communication system, an Automatic Repeat Request (ARQ) scheme and a Forward Error Correction (FEC) scheme are known as error control algorithms. Recently, various HARQ schemes are being developed as the technology used for controlling errors by combining the ARQ scheme and the FEC scheme.
The simplest HARQ scheme is a Chase Combining (CC) scheme. In the CC-based HARQ scheme, a decoder combines a plurality of received encoded packet copies when the copies of an encoded data packet are transmitted. The CC scheme can provide diversity gain and can be easily implemented.
Another HARQ scheme is an Incremental Redundancy (IR) scheme. When decoding fails at the first attempt, additional redundant information is transmitted in place of a copy of a total encoded packet.
Recently, a large amount of research is being conducted on the CC-HARQ and IR-HARQ based on a LDPC code. Conventionally, it is known that the IR-HARQ outperforms the CC-HARQ.
However, because a performance of the IR-HARQ scheme based on the LDPC is determined by a puncturing algorithm of the LDPC code, the development of an LDPC puncturing algorithm is mandatory, which can minimize performance degradation due to puncturing. Unfortunately, all of the code rates are not supported because an LDPC code puncturing process is performed in a block unit in the conventional IR-HARQ scheme based on the LDPC.